.\"	$OpenBSD: ltrace.1,v 1.6 2015/03/13 19:58:41 jmc Exp $
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.\" Copyright (c) 2013 Miodrag Vallat.
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.\"	from: @(#)ktrace.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: March 13 2015 $
.Dt LTRACE 1
.Os
.Sh NAME
.Nm ltrace
.Nd shared library function call tracer
.Sh SYNOPSIS
.Nm ltrace
.Op Fl ai
.Op Fl f Ar trfile
.Op Fl t Ar trstr
.Op Fl u Ar trspec
.Ar command
.Sh DESCRIPTION
.Nm ltrace
enables shared library function calls issued by the specified processes
to be traced using the
.Xr utrace 2
user tracing facility.
By default, call trace data is logged to the file
.Pa ktrace.out ,
unless overridden by the
.Fl f
option.
Each function call is traced as a pair of
.Dv KTRFAC_USER
entries;
the first entry contains the shared library containing the symbol being
called, and the second entry contains the symbol name.
.Pp
Once tracing is enabled on a process, trace data will be logged until
either the process exits or the trace point is cleared with
.Xr ktrace 1 .
A traced process can generate enormous amounts of log data quickly;
it is strongly suggested that users memorize how to disable tracing before
attempting to trace a process.
The following command is sufficient to disable tracing on all user owned
processes and, if executed by root, all processes:
.Pp
.Dl $ ktrace -C
.Pp
The trace file is not human-readable; use
.Xr kdump 1
to decode it.
.Pp
The options are as follows:
.Bl -tag -width 9n
.It Fl a
Append to the trace file instead of recreating it.
.It Fl f Ar trfile
Log trace records to
.Ar trfile
instead of
.Pa ktrace.out .
.It Fl i
Inherit; pass the trace flags to all future children of the designated
processes.
.It Fl t Ar trstr
The string argument represents the kernel trace points, one per letter.
The default flags are
.Cm c ,
.Cm e ,
.Cm i ,
.Cm n ,
.Cm s ,
.Cm t ,
and
.Cm u .
The following table equates the letters with the tracepoints:
.Pp
.Bl -tag -width flag -offset indent -compact
.It Cm c
trace system calls
.It Cm e
trace emulation changes
.It Cm i
trace I/O
.It Cm n
trace namei translations
.It Cm s
trace signal processing
.It Cm t
trace various structures
.It Cm u
trace user data coming from
.Xr utrace 2
.It Cm w
trace context switch points
.It Cm +
trace the default points
.Pq everything but context switch points
.El
.It Fl u Ar trspec
Restrict the trace to a list of shared objects and/or function names, as
specified by the
.Ar trspec
argument.
The trace specification is a comma-separated list of library names,
followed by a colon
.Pq :\& ,
and a comma-separated list of function names.
Each list can be empty.
Each list member may end with a star
.Pq *
to only match the beginning of a name.
An exclamation mark at the beginning of a list turns it into a rejection list,
causing all unmatched names to be traced.
Library names are compared without their version number and
.Sq .so
suffix.
.It Ar command
Execute
.Ar command
with the specified trace flags.
.El
.Sh FILES
.Bl -tag -width ktrace.outXXX -compact
.It Pa ktrace.out
Default
.Nm
dump file.
.El
.Sh EXAMPLES
Trace all shared library function calls from
.Xr wc 1
reading the message of the day:
.Dl $ ltrace wc -lh /etc/motd
.Pp
Trace only the shared library function calls in
.Pa libutil.so :
.Dl $ ltrace -u libutil wc -lh /etc/motd
.Pp
Trace all the shared library function calls but those in
.Pa libc.so :
.Dl $ ltrace -u \(dq!libc\(dq wc -lh /etc/motd
.Pp
Trace all the shared library function calls with names starting
.Qq fmt :
.Dl $ ltrace -u \(dq:fmt*\(dq wc -lh /etc/motd
.Pp
Trace all shared library function calls, as well as all system calls:
.Dl $ ltrace -t cu wc -lh /etc/motd
.Sh SEE ALSO
.Xr kdump 1 ,
.Xr ktrace 1 ,
.Xr ktrace 2 ,
.Xr utrace 2
.Sh HISTORY
The
.Nm ltrace
command appeared in
.Ox 5.4 .
